The present invention concerns a method called a sequential method for controlling a sliding moving panel driven by an electric motor, wherein the signal originating from an optical fibre pressure sensor is exploited in a sequential manner to stop and reverse the operating direction of the driving motor in the event of a variation in said signal, and wherein the frequency measurement of the pulses generated by an encoding device is exploited to perform pre-detection of an obstacle and to determine the end of travel positions of the moving panel.
The invention also concerns a safety device for such a moving panel including means for detecting the presence of a foreign body braking said moving panel""s movement and preventing it from closing completely.
The invention also concerns an optical fibre force sensor able to be used in particular in safety devices of the aforementioned type.
Finally, the object of the invention is to provide a method for calibrating the aforementioned direct and indirect detection means which allows the reliability of the operation of the sensor to be increased.
Automobile vehicles are increasingly fitted with electric windows, i.e. systems wherein the windows are driven so as to slide in the opening direction or the closing direction by an electric motor whose operation is controlled by the driver of the vehicle by means of a manual switch. Such systems have allowed substantial progress to be made as regards automobile safety, insofar as the driver can easily open or close the windows while continuing to pay attention to traffic conditions and to driving the vehicle. These systems have, however, significant problems as to reliability which are often linked to the appearance of current peaks when the motor driving the window is stopped too abruptly. It is known that any obstacle blocking the movement of the window generates current peaks in the motor which are generally damaging, particularly for certain components, such as the control relays or the switching transistors. Such peaks can appear, for example, when the driver continues to activate the switch which controls the operation of the driving motor when the window has already reached the closed position in which it is pressed against the door frame. Current peaks can also appear when a foreign body, for example an arm, is resting on the edge of the window and prevents the latter from moving upwards.
In order to overcome the aforementioned difficulties, a known solution consists in measuring the maximum level of the supply current provided to the driving motor, and blocking said current above a predetermined threshold. This measurement is generally performed across the terminals of a switching transistor whose resistance varies from one component to another and remains dependent upon the temperature. Other methods use precision resistors (current measurements) or Hall effect sensors (magnetic field measurements), but the cost price of such components is high.
Another control method, which is less expensive and more efficient, consists in detecting the pulses caused by the switching of the driving motor brushes. These pulses are superposed with the direct consumption current of the motor, and their frequency is proportional to the speed of the rotor. A technique of this type is described in U.S. Pat. No. 4,870,333 in the name of the Sidosha Denki Kogyo company which proposes a method for controlling electric windows for automobile vehicles wherein the number of pulses generated by the operation of the electric motor driving the window is stored in a counter. When the number of pulses stored in the counter reaches a maximum predetermined value, the control device which operates the system concludes that the window has reached the fully open position and causes the driving motor to stop. Conversely, when the window moves up, the number of pulses stored in the counter is reduced by one unit per revolution of the driving motor. When this number becomes equal to zero, the system concludes that the window has reached the closed position in which it presses against the door frame, and again stops the driving motor.
The main drawback of the above system is that the speed at which the window rises is not constant and depends on numerous parameters such as the drive torque of the motor, the friction between the window and the door frame, the speed and trajectory of the vehicle, etc. Consequently, the position of the window cannot be calculated with sufficient accuracy for the moment at which the window is completely closed to be determined exactly. With such a method, one can at most determine an end of travel zone in which one knows that the window is close to the door frame. The driving motor can, consequently, be stopped on the command of the control device before the window is completely closed. Conversely, the window can continue to be supplied with current when the window is already completely closed, which generates current peaks which are damaging to the motor and the electronic control circuit. On the other hand, nothing in the Sidosha patent is provided for detecting, prior to pinching, an overload which would form an obstacle to the progress of window. Finally, nothing is provided for detecting the presence of a foreign body such as a child""s hand, the thickness of which is equal to or less than the end of travel zone. Thus, during the automatic closing of moving panels, such as, in particular, an automobile vehicle window, one has to try to assure safety by preventing a foreign body such as, for example, an arm or a hand, being caught between said window and the door frame against which it has to be pressed. For this purpose, in the event that something is caught, a safety device stops the driving or reverses the direction of movement of the window. Among known safety devices, one solution consists in incorporating an electromagnetic wave guide, for example an optical fibre, inside the sealing gasket into which the window is guided. An emitter, for example a laser diode, injects a light signal at the end of the fibre. This signal propagates up to a receiver, for example a photodiode, placed at the other end of the fibre. In the event of an incident, the foreign body is driven by the window as it moves upwards towards the sealing gasket and exerts pressure on the optical fibre. By the effect of the pressure, the optical fibre is deformed, which causes a local modification in its radius of curvature. This modification in the fibre""s radius of curvature causes significant losses, and consequently a drop in the amplitude of the optical signal picked up by the receiver. There results a drop in the amplitude of the electric signal transmitted by the receiver to a control circuit, which, in response to this drop, produces a stop or direction reversal signal for the motor driving the window.
A safety device associated with the sliding window of the door of an automobile vehicle is known from German Patent No. DE 44 16 803. This device includes a magnet arranged on the shaft of the electric motor driving the window with which is associated a Hall effect sensor. As a function of the signals transmitted by the Hall effect sensor, a microprocessor can determine that the window has reached its completely closed position. The microprocessor can also detect a reduction in the speed at which the window moves upwards due to the effect of the presence of a foreign body, and can command the reversal of the direction of movement of said window to avoid anything being caught therein. In addition to this indirect detection device, the safety device includes a direct detection device including a pressure sensor arranged in the door frame.
The main drawback of the above safety device lies in the fact that the indirect detection means continue to be used as obstacle detection means even when the window comes in proximity to its completely closed position. It has already been stated that the speed at which the window moves upwards is not constant and that it depends on numerous parameters. Thus, if because of measuring inaccuracies, the microprocessor does not indicate that the window is closed while the latter is in fact closed, said microprocessor will interpret this situation as a situation in which something is caught, and will command the driving motor to stop and reverse its working direction. It becomes impossible at this moment to close the window.
The safety devices of the type described hereinbefore which use optical fibre pressure sensors as obstacle detectors have numerous drawbacks both as regards their industrial manufacture and as regards their performance with the user. These safety devices must, in fact, be produced on a large scale to satisfy the demands of the market, such as the automobile market. This thus assumes a manufacturing method which is both simple and quick with inexpensive components and materials. The same is true for the test and calibration procedures which must be quick and which allow the direct and indirect detection means to keep their operating features over time. As will be seen in the following description, it is difficult, in such conditions, to obtain products with homogenous features.
A first problem is linked to the fact that it is difficult to be able to have available large quantities of low cost optical sources having features which have little scattering. This concerns in particular the power and transmission angle as well as the radiation spectrum of such sources.
A second problem is linked to the fact that the optical fibre used in the sensor has to be fixed to the optical source either by means of specific connectors or more simply by bonding. This requires several operations for preparing the ends of the fibre (stripping off the coating, breaking or polishing), centring the fibre with respect to the optical source, and finally fixing by means of quick setting resins. Large scale manufacture necessarily involves significant dispersion of the power injection output in the fibre, which affects the performance of the sensor.
As described hereinbefore, optical fibre sensors mostly work on the principle of losses induced by the variation in the radius of curvature of said fibre by the effect of pressure. The setting in place of the fibre and preparation of the sensitive part of the sensor thus necessarily introduce dispersion in the stresses in the optical fibre, which leads to dispersion in the performance of the sensors.
It can also be noted that the performance of the sensors greatly depends on the conditions in which they are used, and their environment. This is the case, for example, of automobile applications where the sensors have to operate within ambient temperature ranges comprised between xe2x88x9240xc2x0 C. and +85xc2x0 C. It is clear that, in such conditions, the features of certain components such as the optical source cannot remain constant (emission power and spectral field). The same is true for the power injection output in the fibre which greatly depends on the thermal properties of the materials used for the source-fibre connection.
The problem is all the more significant as regards the sensitive part of the sensor. Assuming that the optical fibre is not itself sensitive to temperature variations, the materials which are used as support and sheath, generally polymers, can undergo thermal stress, which results in pressure variations applied to the fibre. These effects, to which is added the intrinsic sensitivity of the optical fibre to the temperature, can cause variations of more than 80% in the output signal.
Finally, in addition to the problems linked to the conditions of use of the sensor, there are the inevitable variations in the features of the latter caused by normal wear of the materials and components.
The list of the aforementioned problems shows the difficulties which have to be overcome in order to be able to manufacture on a large scale and at a low cost optical fibre pressure sensors which can be used as obstacle detectors. Sensitivity to certain disturbances as well as wear phenomena mean that the original calibration cannot be kept. This results in problems of reliability and even, in certain cases, non operation of the safety devices using such sensors.
The object of the present invention is to overcome the aforementioned problems and drawbacks by providing a reliable safety device for driving and closing sliding panels electrically powered.
The invention thus concerns a sequential control method for a moving panel which is driven so as to slide in a frame by an electric motor, including the steps of:
detecting by first means the presence of a foreign body capable of preventing the complete closing of said moving panel by becoming caught between said panel and the frame inside which said panel slides;
measuring by second means the frequency of the pulses caused by the rotation of the electric motor driving the moving panel;
generating an alarm signal when the presence of the foreign body is detected;
stopping, then reversing the working direction of the electric driving motor on reception of the alarm signal; and
stopping the driving motor or reversing its working direction when the frequency of the pulses becomes substantially zero in the absence of the alarm signal.
Thus, when the window is closed, one can deduce that in the absence of the alarm signal, the window abuts against the door frame and that any risk of accident has been avoided. Conversely, in the case of the alarm signal, the reversal of the working direction of the driving motor is immediately commanded. As a result of these features, the sequential detection method according to the invention simultaneously allows personal safety to be increased and the electrical and electronic parts to be protected efficiently against current peaks.
According to another feature of the method of the invention, the frequency of the pulses caused by the rotation of the electric motor driving the panel is measured, and said motor is stopped or the working direction thereof is reversed when the frequency of said pulses becomes less than a predetermined frequency threshold.
According to another feature of the method, the presence of a foreign body capable of preventing the complete closing of the moving panel is detected using an optical fibre pressure sensor.
According to another feature of the method, one deducts from the measurement of the number of pulses caused by the rotation of the electric driving motor an indication of the travel of the moving panel from a previously known reference position, and one commands a speed deceleration ramp of the driving motor, when the moving panel reaches an end-of-travel zone.
According to another feature of the method, when the moving panel reaches the end-of-travel zone, the means used to measure the frequency of the pulses caused by the rotation of the electric motor are no longer used for detecting the presence of an obstacle capable of preventing the complete closing of the moving panel, but are only used for determining the position of said panel relative to the frame into which it slides.
According to another feature of the method, the reference position is the last calculated position of the moving panel prior to the stopping of the driving motor.
The measurement of the number of pulses caused by the rotation of the driving motor allows the travel of the moving panel to be calculated from a previously known reference position. In the case of an automobile vehicle, because of the inertial forces due to jerks, the effects of friction and slipping, the indirect determination of the position of the window has a certain error rate. This error rate is cumulative. Thus, after ten attempts at moving the window downwards and upwards, the cumulative space between the calculated position and the real position of said window is of the order of one to two centimetres. However, this error remains sufficiently reliable to allow an end-of-travel zone to be defined for the downward and upward movements of the window, a zone in which said window is in proximity to the door frame against which it has to be applied. The delay time due to the variation in current with respect to the rotational speed of the motor is advantageously used to limit current peaks and to protect the motor and its control unit efficiently.
The invention also concerns a method for controlling a moving panel driven so as to slide by an electric motor, characterised in that it consists in measuring the frequency of the pulses caused by the rotation of the electric motor driving the moving panel, and in stopping or reversing the working direction of said motor when the frequency of such pulses becomes less than a predetermined frequency threshold.
Since the frequency of the pulses is proportional to the rotational speed of the driving motor, it becomes possible to detect the presence of an obstacle braking the movement of the closing panel and preventing it from moving upwards. This is the case, for example, of the action of an arm placed on the edge of an automobile vehicle window. The comparison of this measured speed with a reference speed thus allows pre-detection of an obstacle and, in certain cases, prevents such obstacle being caught. It also allows the current peaks which are particularly damaging, especially for the driving motor electronic control circuit, to be considerably reduced.
The invention also concerns a safety device including means for detecting the presence of a foreign body braking the movement of a moving panel driven so as to slide by an electric motor and preventing it from closing, characterised in that said detection means are of the indirect type, based on the measurement of the frequency of the pulses caused by the rotation of the electric motor.
According to another feature of the invention, the aforementioned indirect type of detection means are associated with second means for directly detecting the presence of a foreign body, these means including a pressure sensor formed by an optical fibre associated with means for transmitting and receiving optical signals propagating within said fibre.
Another object of the present invention is to provide an optical fibre pressure sensor which can be used as an obstacle detector keeping its original calibration despite its sensitivity to physical disturbances such as the temperature and to the wear phenomena of the materials of which it is formed.
The invention therefore also concerns a method for calibrating an optical fibre pressure sensor used as an obstacle detector in a drive system for an electrically sliding moving panel, the sensor including an emitter supplied with electric power which injects a light signal into an optical fibre, the light signal propagating up to a receiver which transmits, in response to the light signal transmitted by the optical fibre, an electric signal to a control unit with a microcontroller and/or a microprocessor which analyses the data originating from said receiver and, in the event of an incident, allows the electric motor driving the moving panel to be stopped or the working direction thereof to be reversed, the method being characterised in that during the periods in which it is observed that the motor driving the moving panel has stopped, the operating parameters of the pressure sensor are compared and corrected, taken in any environmental conditions, as a function of the same parameters of a standard sensor taken in known reference conditions stored in a non volatile memory which is accessible to the microcontroller and/or the microprocessor of the control unit.
As a result of these features, the pressure sensor calibration method begins as soon as the stopping of the motor driving the moving panel is observed. Preferably, the operating parameters of the sensor are measured and corrected repeatedly during the entire duration of the stopping time of said driving motor. During the motor operating periods, only the last corrections of the pressure sensor operating parameters stored in the memory are taken into account. The performances of the pressure sensor can thus be kept, despite wear phenomena and the existence of physical disturbances to which the sensor is sensitive.
According to a first implementation variant, the method of the invention includes the steps of:
cutting off for a short instant the emitter""s electric supply current as soon as it is observed that the motor driving the moving panel has stopped;
measuring the offset level of the electric signal transmitted by the receiver, then resetting its value to zero;
supplying the emitter again by means of a constant direct electric current I0; and
measuring the output level VS of the receiver, and allocating it a coefficient k such that kVS=VR, where VR is a known reference level of a standard sensor taken in known reference conditions.
According to a second implementation variant, the method of the invention includes the steps of:
supplying the emitter by means of a periodic rectangular current;
measuring the high output level VS of the receiver as well as its variation xcex94VS, and
performing the operation VS (xcex94VS/xcex94VR)=Vxe2x80x2S and determining the coefficient C=VRxe2x88x92VSxe2x80x2 so that
VSxe2x80x3=VR, where VR and xcex94VR are known reference values of a standard sensor taken in known reference conditions, the ratio xcex94VS/xcex94VR is the pressure sensor sensitivity correction coefficient, and C is the residual offset correction coefficient of said sensor.
According to another alternative implementation, the method of the invention includes the steps of:
supplying the emitter by means of a periodic rectangular current;
measuring the high output level VS of the receiver as well as its variation xcex94VS;
calculating the pressure applied as a function of the level of the measured signal by means of a polynomial equation of a degree greater than or equal to 1 and whose coefficients are initially determined during a first calibration; and
periodically correcting these coefficients as a function of the measurement results in order to obtain a reliable pressure measurement.
Yet another object of the present invention is to provide a pressure sensor which is simple and inexpensive to manufacture.
The invention also concerns a method for calibrating means for indirectly detecting the presence of a foreign body capable of preventing the complete closing of a moving panel driven so as to slide into a frame by an electric motor, these means allowing the detection of the electric pulses generated by the rotation of the motor and controlling the stopping, then the reversal of the working direction of said motor when the frequency of the pulses becomes less than a threshold frequency, this method being characterised in that it includes the steps of:
measuring, for different positions of the moving panel relative to the frame in which said panel moves, the corresponding frequency of the pulses caused by the rotation of the motor to determine the instantaneous speed of movement of the panel in a given position; and
comparing, for each position of the moving panel, the frequency of the measured pulses to the frequency of the same pulses during the preceding travel of said moving panel so that, if there is a difference between said frequencies and this difference does not exceed a predetermined safety value, the threshold frequency is corrected so that it does not command the stopping and reversal of the working direction of the motor.
Other features and advantages of the present invention will appear more clearly upon reading the following description of an implementation example of the method according to the invention, this example being given purely by way of non-limiting illustration in conjunction with the annexed drawings, in which: